US RDA
310 to 420 mg daily (age and sex dependent)
Effective dose
300 to 400 mg daily elemental magnesium for supplementation
Upper limit
350 mg from supplements (RDA higher because food-based)
Timing
Evening for sleep support
With food
Optional. Glycinate is well tolerated on empty stomach.
Bioavailability
Glycinate > citrate > oxide (which is largely unabsorbed)
Best forms to buy
Glycinate
Best absorbed, calming, doesn't cause loose stools
Citrate
Good for constipation, mild laxative effect
L-threonate
Crosses blood-brain barrier, cognitive focus
Oxide
Avoid, poorly absorbed
Signs of deficiency
- · Muscle cramps
- · Insomnia
- · Anxiety
- · Constipation
- · Migraines
Drug interactions
- · May reduce absorption of some antibiotics and osteoporosis medications
- · Diuretics can deplete magnesium
Toxicity
Diarrhea at high doses is the first sign. Cardiac risk only with kidney disease.